Description:
<jats:p>The dc conductivity of a sintered sample of Y<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> containing an excess of lower‐valent metal (Ml) impurities has been measured at 600° to 1100°C in air as a function of the water vapor pressure (0.4 to 3000 Pa). The logarithm of the <jats:italic>p</jats:italic>‐type conductivity vs log <jats:italic>P</jats:italic><jats:sub>H2o</jats:sub> has a slope of – 1/2 in certain regions of <jats:italic>F</jats:italic><jats:sub>H2o</jats:sub> and temperature. This reflects a defect situation where interstitial protons from water vapor balance the excess of lower‐valent cation impurities: [H<jats:sub>˙</jats:sub>] = [M1<jats:sub>′</jats:sub>]. The activation energy for the <jats:italic>p</jats:italic>‐type conductivity under these conditions is evaluated and interpreted in terms of the enthalpy needed to dissolve interstitial protons in yttria.</jats:p>